main.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
>
<TextView
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:text="@string/hello"
/>
<ProgressBar
android:id="@+id/progressBar"
style="?android:attr/progressBarStyleHorizontal"
android:layout_width="200dp"
android:layout_height="wrap_content"
android:visibility="gone"
/>
<Button
android:id="@+id/startButton"
android:layout_width="65dp"
android:layout_height="36dp"
android:text="start"
/>
</LinearLayout>
BarHandlerActivity.java
package archie.android.handler;
import android.app.Activity;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.ProgressBar;
public class BarHandlerActivity extends Activity {
private Button startButton;
private ProgressBar progressBar;
private static final String TAG="tag";
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
startButton=(Button) findViewById(R.id.startButton);
progressBar=(ProgressBar) findViewById(R.id.progressBar);
startButton.setOnClickListener(new ButtonListener());
}
class ButtonListener implements OnClickListener{
@Override
public void onClick(View v) {
progressBar.setVisibility(View.VISIBLE);
updateBarHandler.post(updateThread);
}
}
//使用匿名内部类来复写Handler当中的HandleMessage方法
Handler updateBarHandler=new Handler(){
@Override
public void handleMessage(Message msg) {
//从消息队列中得msg的一个成员
progressBar.setProgress(msg.arg1);
updateBarHandler.post(updateThread);
super.handleMessage(msg);
}
};
//线程类，该类使用匿名内部类的方式进行声明
Runnable updateThread=new Runnable() {
int i=0;
@Override
public void run() {
Log.v(TAG, "Begin Thread");
i=i+10;
//得到一个消息对象，Message类是由Android操作系统提供
Message msg=updateBarHandler.obtainMessage();
//将msg对象的arg1参数的值设置为i
//用arg1和arg2两个成员变量传递消息，系统性能消耗少
msg.arg1=i;
try{
Thread.sleep(1000);
}catch(InterruptedException e){
e.printStackTrace();
}
//将msg对象加入到消息队列中
updateBarHandler.sendMessage(msg);
if(i==100){
//如果当i的值为100时，将线程对象从handler中移除
updateBarHandler.removeCallbacks(updateThread);
}
}
};
}
